Lead author Wendy Cadge, a sociologist at Brandeis University in Waltham, Mass., found that the prayers fell into one of three categories -- about 28 percent of prayers were requests of God, 28 percent were prayers to both thank and petition God, while another 22 percent of the prayers just thanked God.

Some say they are sure God exists and others pray simply to cover the bases. Some pray for big things -- to stay healthy, keep employed and to strengthen relationships -- but some pray to find parking spaces and missing items.

The study, published in Poetics, analyzed 683 prayers written in a public prayer book placed in the rotunda of the Johns Hopkins University Hospital in Baltimore from 1999 to 2005.

The study found that prayer writers seek general strength, support and blessing from their prayers, rather than explicit solutions to life's difficult situations.

"If researchers studying religion and health take seriously even the possibility that prayer may influence health, they need to learn more about what people pray for, how they pray, and what they hope will result from their prayers," Cadge said in a statement.